"White Dwarf" is a magazine made by Games Workshop to showcase their miniatures. This is an important point since you have to understand that while the magazine has few ads, what ads there are is for Games Workshop models only and all content within showcases their models. So it's more like a catalog with articles.
That said, the articles are quite useful for anyone new to the hobby. There are always lots of pictures, ranging in quality from slightly-above-average to masterpieces, a collection of magazines shows the progression a new painter might make while he's in the wargaming hobby. Other articles focus on aspects of the game such as sample battles or battle reports. These are equally wonderful if you're into the gaming side of the hobby. For those into the painting or modelling, they have plenty of articles showing how to paint a certain thing a certain way or how to model your own fun additions to Games Workshop's impressive models.
All in all, the magazine is a perfect read for anyone new to the hobby. I recommend it for the new guys since if you've been in the hobby for a little while things start to get repetitive - you can only say so much about painting small figures.